This invention relates to an improved water heater equipped with an infrared gas burner formed by a perforated ceramic plate.
Residential and commercial water heaters are commonly provided by a vertical cylindrical water tank with a gas burner below the tank. While the burner has been designed in several forms, all the burners found in conventional water heaters burn the gas with a flame; as known, flame-type burners receive combustion air partially as primary air that is inspirated by the gas stream and partially as secondary air that flows into the flame.
In spite of the many years during which conventional water heaters have been undergoing improvement, there is still a need for improving combustion to minimize the formation of air-polluting nitrogen oxides (NO.sub.x), and for simplifying the construction of the water heater to reduce its cost.
As far back as September, 1963, Research Bulletin 97 (32 pages) was issued by American Gas Association Laboratories on Some New Or Unusual Methods For Heating Water With Gas. Bulletin 97 included tests on infrared burners which are commonly referred to as flameless burners and which receive all of the combustion air as primary air. The infrared burners were formed by triple layers of nickel stainless steel screen as the burner face attached to a pan-type burner body with one or two venturi injection tubes attached to the bottom of the pan-type body. Warpage of the screens was encountered and this led to flashback. Another problem was the flow of heat from the radiant screens to the metal pan-type burner body. Carbon monoxide measurements of the combustion products were in the several 100 parts per million range. There were no NO.sub.x measurements. Thirty years later, the marketplace still lacks a water heater featuring an infrared burner capable of yielding combustion products or flue gas containing very low levels of air-polluting NO.sub.x.
A principal object of this invention is to provide a water heater with an infrared gas burner capable of producing a flue gas containing very small amounts of NO.sub.x.
Another important object is to provide a durable infrared burner of simple construction.
A further object is to integrate the construction of the water heater and the infrared burner thereof to achieve overall economies of manufacture.
These and other objects and advantages of the invention will be evident from the description which follows.